1. Field of the invention
The present invention relates to a tape cassette and, more particularly, to a video tape cassette.
2. Description of the Prior Art
Some video tape recorders accept two different sizes of video cassettes, a standard size video cassette 21, such as shown in FIG. 1, and a reduced size video cassette 22 such as shown in FIG. 2. The standard size video cassette has size such that the distance between opposite sides is A and the distance between the centers of the tape reels 1 is L, whereas the reduced size video cassette has a size such that the distance between opposite sides is B, which is shorter than the distance A, and the distance between the centers of the tape reels 6 is L, which is the same as that of the standard size video cassette.
As shown in FIG. 1, standard size video cassette 21 has a casing 2 defined by a top shell 2a and a bottom shell 2b which are closed together to provide a cassette cavity therein to store the tape wound on tape reels. A front face of cassette 21 has an opening 3 past which a magnetic tape 4 extends. A lid member 5 is provided on opening 3 to cover the tape when the tape is not in use.
Similarly, as shown in FIG. 2, reduced size cassette 22 has a casing 7 defined by a top shell 7a and a bottom shell 7b. An opening 8 is provided at the front face of cassette 22 past which tape 9 extends, having the same tape width as tape 4, thereacross and has a lid member 10 to cover the tape when the tape is not in use.
The standard size cassette has a groove 2c formed on the outer surface of the bottom shell 2b and extending straight between the front and back faces. Similarly, the reduced size cassette has a groove 7c formed on the outer surface of the bottom shell 7b. The grooves 2c and 7c have about the same width and the same depth. For example, if the thickness of the wall forming the bottom shell is about 2 millimeters, the depth of the groove is about 1.5-1.7 millimeters.
When in use, the video cassette is loaded in a video tape recorder by inserting the cassette in a cassette holder 11, such as shown in FIGS. 3 and 4. Cassette holder 11 is defined by a bottom plate 11c and opposite side plates 11a. The cassette holder may have a top plate, such as shown in FIGS. 5 and 6. Cassette holder 11 further has a projection 11b mounted on the bottom plate 11c and extending parallel to the side plates 11a. The width and the height of the projection is about the same as the width and the depth of the groove. Thus, in the case of the above example, the height of the projection is, at maximum, about 1.4 millimeters.
As shown in FIG. 5, when inserting the standard size cassette into the cassette holder, the cassette is held in position by the opposite side plates 11a receiving the opposite sides of the cassette and, at the same time, by projection 11b engaging groove 2c.
As shown in FIG. 6, when inserting the reduced size cassette into the cassette holder, the cassette is held in position by projection 11b engaging groove 7c. Since the reduced size cassette is inserted in the cassette holder with spaces left at opposite sides, one may need to move the cassette right and left before it is properly positioned in the cassette holder, or the projection may engaging a non-grooved area.
The problem the prior art cassettes is in that during the insertion and ejection of the cassette from the cassette holder, projection 11b slidingly engages the groove resulting in the wearing of the inner face defining the groove. This not only further results in the loose engagement with projection 11b, but also in producing undesirable powder from the wall of the groove. Such powder adheres on the magnetic tape to markedly deteriorate the picture quality such that image drop out occurs very often. The generation of the powder may be suppressed by grinding the edges of projection 11b, but it is very difficult to provide a smooth finish of the projection having such a small dimension.